1. Field of the Invention
The present invention relates generally to a high efficiency gas engine driven cooling system, and more particularly to a liquid chiller, or an air cooling system, driven by a gas fueled internal combustion engine, and having means to recover the waste heat energy usually rejected into the atmosphere from the refrigeration heat cycle, and from the internal combustion heat cycle, to produce useful electric power.
The generated electric power is transmitted to drive the auxiliary pumps, fans, and controls of the cooling system, thus reducing the energy needed, and increasing the fuel utilization.
1. Description of Prior Art
The continuing increases in the cost of fossil fuel, and the increased environmental concerns, have forced global attention on a variety of energy conserving, and waste energy based co-generation technologies.
In the U.S. electric power utility generation peaks during the summer months. Refrigeration, and air cooling systems accounts to more than 40 percent of the electric power daily demand, and approximately 25 percent of the peak demand comes from commercial cooling. The increased charges for the electric use during summer peak demand period is a major issue when making purchase decisions of cooling systems, and has driven the user to reducing the electric peak demand by using absorption cooling, natural gas engine driven cooling, and by co-generation. Many electric utility companies offer incentives to encourage reducing the electric power use during peak demand periods, to avoid very expensive expansions of its utility power plants, and its electric power distribution facilities. Electric and natural gas utility companies recognize that natural gas driven cooling is an important available alternative to effectively decrease the electric power demand, and to contribute to a cleaner environment. Although the first costs are higher for natural gas driven cooling systems, operating cost are significantly lower, and the increased savings from reduced operating costs can pay back the first cost premium in a very short period, and will deliver a reasonable return on the capital investment.
Publications of the Gas Research Institute (GRI) highlighted a growing commercial market in the U.S. for the natural gas engine driven cooling systems, these systems came to the market in 1989, and are commercially available or under development for capacities starting from 15 ton for small roof top units installations, and up to 500 ton liquid chillers for central cooling systems for large building complexes, and industrial applications.
Gas engine driven cooling systems, may be equipped with an automotive derivative engine coupled to a refrigerant gas compressor, the compressor may be of a rotary, helical screw, scroll, centrifugal, or reciprocating type. The inherent variable speed capability of the gas engine drive, provides high efficiency compression over a wide range of cooling loads.
The theory and practice of combined cycle engines are well known for recovering and utilizing heat from liquid cooled internal combustion engines to produce auxiliary power using Rankine Cycle vapor driven turbine or expander. U.S. Pat. No. 4,031,705 by Berg, disclosed an auxiliary power vapor or hot gas engine coupled to an internal combustion engine for generating vapor in one or more heat exchanger to drive a vapor engine.
U.S. Pat. No. 4,996,845 by Kim, disclosed a cooling, heating and power generating device utilizing waste heat from an automobile engine to produce auxiliary energy source for driving various accessories such as cooling/heating apparatus. U.S. Pat. No. 5,000,003 by Wicks disclosed a combined internal combustion engine, and a power vapor turbine or expander to recover virtually all the internal combustion engine heat normally rejected through the engine coolant radiator and through the engine exhaust to generate auxiliary power and provide very substantial fuel efficiency.
It is noted that the prior art work do not suggest an internal combustion engine driven fluid chiller or cooling system wherein the heat energy rejected in the refrigerant condenser is recovered and combined with the heat rejected from the internal combustion engine cooling fluid and from the exhaust gas stream and recovered by another refrigerant power fluid to drive an auxiliary power vapor expander, and achieve a very high utilization of fuel for refrigeration or cooling. In addition to the well known environmental benefits of achieving a higher fuel utilization, the present invention shall provide a very high return on the investment, for example the energy savings from operating a 100 ton gas engine driven fluid chiller system utilizing the present invention when compared to a direct electric driven fluid chiller system, will provide less than two year payback on the investment needed for the improvements described herein.
The present invention is related to my previous U.S. Pat. No. 5,136,854, which disclosed a process for conserving the waste energy usually rejected from the vapor compression refrigeration heat cycle, and also related to my previous U.S. co-pending application Ser. No. 07/887,876 which discloses a process for conserving the waste energy usually rejected from a automotive internal combustion engine heat cycle. However these prior disclosures did not suggest individually, or integrally the system combination of embodiments and details as disclosed in the present invention.
It is therefore, a principle object of the present invention to increase the Energy Efficiency Ratio (EER) of a gas engine driven cooling system.
It is further, a principle object of the present invention to provide an energy recovery system for a gas engine driven cooling system, utilizing the waste heat usually rejected from the engine cooling fluid, and from the exhaust gas stream, to co-generate useful electric power.
It is further, a principle object of the present invention to provide an energy recovery system, utilizing the waste heat usually rejected from the condenser of a refrigerant direct expansion cooling system, to co-generate useful electric power.
It is further, an object of the present invention to provide a natural gas engine driven cooling system, which conserves energy, and reduces the pollution impact on the environment.
It is further, an object of the present invention, to reduce the electric power use during the peak demand periods, to avoid the expensive expansions of the power generation and distribution facilities of the electric power utilities.
These objects, and others which will become apparent from the following detailed descriptions and drawings, are fulfilled by incorporating a heat exchange system to recover the waste heat energy, usually rejected from; (1) the condenser of a refrigerant direct expansion cooling cycle; and (2) from the internal combustion engine block and exhaust manifold, to operate a gas expander-electric generation unit, convert the waste heat energy to Kinetic energy, and to co-generate useful electric power.
While the present invention has particular usefulness in connection with a gas engine driven cooling system, the invented system can be employed with other gasoline, or diesel fueled internal combustion engines for many applications. The invented energy recovery, and electric power co-generation system, may be added to an existing installation, without the need to modify the basic design of the internal combustion engine.